ABSTRACT

To evaluate the effects of the hydride morphology and initial temperature of fuel cladding on the pellet-cladding mechanical interaction failure under reactivity-initiated accident (RIA) conditions, RIA-simulated experiments were performed on high-burnup fuels with stress-relieved annealed (SR) and recrystallized (RX) M-MDA^TM cladding at room and high (~280°C) temperatures. The results demonstrated that the failure-limit trend of RX-cladded fuels being lower than that of SR-cladded fuels for a similar hydrogen content holds up to at least about 700 wtppm. The observation of the fracture surfaces of failed RX cladding suggests a contribution of radially oriented hydrides to the crack formation and/or penetration, which coincides with the aforementioned failure-limit trend. The temperature effect, namely the failure-limit rise at a high temperature, is evident irrespective of the hydride morphology, while the degree of the temperature effect decreases as the hydrogen content increases.

摘要

为了评估在反应性引发事故 (RIA) 条件下燃料包壳的氢化物形态和初始温度对芯块-包壳机械相互作用失效的影响，RIA 模拟实验对经过应力消除退火 (SR ) 和重结晶 (RX) M-MDA ^TM在室温和高温 (~280°C) 下进行覆层。结果表明，对于相似的氢含量，RX 包覆燃料的失效极限趋势低于 SR 包覆燃料的失效极限趋势，保持至少约 700 wtppm。对失效 RX 包层断裂表面的观察表明径向取向的氢化物对裂纹形成和/或渗透的贡献，这与上述失效极限趋势一致。无论氢化物形态如何，温度效应，即高温下的失效极限升高都是明显的，而温度效应的程度随着氢含量的增加而降低。